1. Field of the Invention
This invention is directed to shutters, in general, and to micro-mechanical shutters mounted on transparent substrates and controlled by electro-static forces, in particular.
2. Prior Art
Numerous articles have appeared in technical journals describing how the techniques used to fabricate integrated circuits can be used to make micro-mechanical devices including micro-motors. Micro-motors are extremely small motors powered by an electric field rather than an electro-magnetic field as is the case for conventional electric motors. The typical micro-motor is comprised of a bearing, a rotor, and a stator.
Integrated circuit techniques have also been applied to fabricate devices comprising silicon on transparent insulating substrates. Representative devices include Silicon-On-Sapphire (SOS) and polysilicon on glass. In SOS techniques, a silicon film, the crystalline quality of which approaches that of bulk silicon, has been used to fabricate high performance VLSI circuits. For example, SOS technology has been used to build integrated circuits of considerable complexity, such as 64K static RAMS. While polysilicon on glass is of much lower quality, it has been good enough to fabricate switch transistors for active-matrix liquid crystal displays (AMLCD).
U.S. Pat. No. 5,078,497 (Vuilleumier) describes a micro-mechanical shutter array which is electrostatically operated. This shutter uses latching flaps made of conductive material which are selectively deflected into recesses in the substrate. This device does not have switching transistors or storage capacitors. A twist-type spring acts as a counter force for the electric force. The shutter has only two latching states and, therefore, can be used only for text-type displays, not pictorial displays. Consequently, it lacks an "active matrix" in LCD terminology. Also, the deep recesses do not allow standard planar integrated circuit processing to fabricate these devices.
Silicon integrated circuit technology has been used to create micro-motors. These micro-motors are merely small spinning discs of silicon and as of yet have no practical application.